Until that movie actually exists, we’re left with “Jack the Giant Slayer,” the latest in an already exhausted trend of legend reinventions (“Snow White and the Huntsman,” “Hansel and Gretel: Witch Hunters,” even “Abraham Lincoln: Vampire Hunter”) that, usually, are either dully serious or pathetically unfunny. Or both.

Anyway, you’d think a monk in possession of world-changing magic beans would be more responsible. In the shockingly uninspired, 115-minute 3-D slog “Slayer,” that monk uses the beans to buy a horse from a stranger—with only a quick, non-informative warning about not getting them wet.

The stranger is 18-year-old Jack (Nicholas Hoult, who fared better in “Warm Bodies”), who'd love to protect Princess Isabelle (Eleanor Tomlinson) as one of the king's guardians but doesn't have the noble blood required. But then those beans touch water and the resulting giant beanstalk sends Isabelle skyward into a land of hideous, generic giants. This prompts a climb-and-rescue mission that includes a vanilla knight (Ewan McGregor), the middle-aged, obviously untrustworthy sleaze (Stanley Tucci) whom the king (Ian McShane) senselessly wants his daughter to marry and Jack, who shares Isabelle's thirst for adventure and, uh, aversion to death.

Otherwise their relationship ain't squat, and they have even less chemistry.

Directed by Bryan Singer (“X-Men”) from a script insufficiently rewritten by Singer's “Valkyrie” writer Christopher McQuarrie, “Slayer” barely has the seed of an idea. The film rips off “Lord of the Rings” with a crown whose possession rules over the giants. Also stolen: numerous lousy visual elements from “Clash of the Titans” and action sequences from “Jurassic Park” and “The Fugitive.”

Just because a movie's big doesn't mean it has real size. Rather than bring a legend to life, the bland, PG-13 “Jack the Giant Slayer” downscales an unforgettable journey into the shrug-worthy muck of every other big adventure, comprising one anti-climactic moment after another. The beans may as well be sleeping pills.

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